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2.2 Reading Resource #3: 
Cell components 
 
Lysosomes 
Lysosomes serve as the cell's "garbage disposal" in animal cells. Proteins, polysaccharides, lipids, 
nucleic acids, and even worn-out organelles can all be broken down by the digestive enzymes found in 
lysosomes. Lysosomes are crucial for organelle recycling and the breakdown of the food that single-celled 
eukaryotes consume. Compared to those found in the cytoplasm, these enzymes are more acidic and active at 
much lower pH levels. The benefit of compartmentalizing the eukaryotic cell into organelles is clear because 
many cytoplasmic reactions would not be able to take place at a low pH. 
 
Figure 24.
A macrophage has formed a vesicle out of a potentially harmful bacterium.. 
Ribosomes 
The cellular components known as ribosomes are in charge of protein synthesis. Free ribosomes can 
be seen in the cytoplasm as either clumps or a single tiny dot under an electron microscope. Both the 
cytoplasmic and endoplasmic reticulum cytoplasmic sides of the plasma membrane are possible locations for 
ribosome attachment. The existence of large and small subunits in ribosomes has been demonstrated by electron 
microscopy. The complex enzymes known as ribosomes are in charge of producing proteins. 
Mitochondria 
Mitochondria (singular = mitochondrion) are often called the “powerhouses” or “energy factories” of 
a cell because they are responsible for making adenosine triphosphate (ATP), the cell’s main energy-carrying 
molecule. The formation of ATP from the breakdown of glucose is known as cellular respiration. Mitochondria 
are oval-shaped, double-membrane organelles (Figure 25) that have their own ribosomes and DNA. A 
phospholipid bilayer with proteins embedded makes up each membrane. Cristae, or folds, in the inner layer 
increase the inner membrane's surface area. The folds' immediate surroundings are referred to as the 
mitochondrial matrix. Different functions of the matrix and cristae are involved in cellular respiration. 

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